A thyristor is a type of semiconductor element that has a pnpn structure and that performs a switching operation. Specifically, it is an important high-power control element. For example, FIG. 6 is a cross-sectional view illustrating a semiconductor thyristor of the prior art. Here, in p-type semiconductor substrate 100, first n-type semiconductor region 101 (N1) is formed. In the top layer of said first n-type semiconductor region 101, element separating insulating film 102 is formed.
In prescribed regions in said first n-type semiconductor region 101, at a prescribed depth, second n-type semiconductor region 103 (N2) and first p-type semiconductor region 104 (P1) are formed. In addition, in the top layer of second n-type semiconductor region 103, second p-type semiconductor region 105 is formed as anode AN. Also, in the top layer of first p-type semiconductor region 104, in the regions separated by element separating insulating film 102, third p-type semiconductor region 107 as gate G and third n-type semiconductor region 108 as cathode CA are formed.
Also, first interlayer insulating film 110 made of silicon oxide or the like is formed over the entire surface to cover second p-type semiconductor region 105, third p-type semiconductor region 107 and third n-type semiconductor region 108. Contact holes CT1 are formed to reach second p-type semiconductor region 105, third p-type semiconductor region 107 and third n-type semiconductor region 108. First electroconductive layer 111 is buried therein, and second electroconductive layer 112 is formed on first interlayer insulating film 110 and connected to said first electroconductive layer.
Also, second interlayer insulating film 113 made of silicon oxide is formed to cover them. Contact holes CT2 are opened to reach second electroconductive layer 112, etc.; third electroconductive layer 114 is formed and buried, and fourth electroconductive layer 115 is formed on second interlayer insulating film 113 and connected to it.
As explained above, said thyristor has three terminals, that is, anode AN made of the p-type semiconductor and cathode CA made of the n-type semiconductor at the two ends of the pnpn structure, and gate G made of the p-type semiconductor sandwiched between them. For example, by sinking current to gate G, holes are injected from anode AN and electrons are injected from cathode CA, so that the thyristor is turned on. When the thyristor with said structure is turned off from the on state, a certain amount of time is required to evacuate the holes that were injected into first n-type semiconductor region 101, so that the turn-off time is increased, which is undesirable.
The purpose of the present invention is to solve the aforementioned problems of the prior art by providing a semiconductor device having a thyristor with a reduced turn-off time, and its driving method.